Thanks for bringing this to our notice. In earlier version of CanvasJS user had access to internal methods and variables which has been kept private from version 1.8. But in the future versions, we are planning to give user structured internally calculated values such as minimum and maximum. As of now, if you know the maximum value suiting to your requirement, you can set it for axisY2 and after that e.chart.options.axisY2.maximum will be available.